What is AED (automated external defibrillator)?

An automated external defibrillator (AED) is a lightweight, portable, battery-operated medical device that checks the heart's rhythm and can deliver an electric shock to help restore a normal rhythm in a person experiencing sudden cardiac arrest.

The device analyzes the heart rhythm automatically and guides the operator with prompts, so even an untrained bystander can use one in an emergency. AEDs can be semi-automated, prompting the user to press a button to deliver a shock, or fully automated, delivering the shock without user intervention. They are commonly placed in schools and other public spaces because rapid use alongside CPR can improve survival from cardiac arrest.

Defined from authoritative sources

This definition is drawn from the sources below, last verified 2026-06-23. How we verify.

1. NHLBI (NIH): Defibrillators verified 2026-06-23
2. FDA: Automated External Defibrillators (AEDs) verified 2026-06-23

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